This invention relates to machines for pre-forming and stiffening flexible sheet material. It is particularly concerned with providing improved machines for forming and stiffening upper materials constituting the end portion of footwear. Accordingly, in one aspect, this invention is directed to implementation of the method for forming in situ thermoplastic counter portions as disclosed in the patent application above cited. It will be understood that usage of the present invention is not limited to footwear manufacture although this field will herein serve for purposes of illustration of the invention.
It has long been an objective in shoe making to shape and stiffen end portions of shoe uppers. As regards their backparts, for instance, counters have been provided for this purpose. They are expensive, costly to install, and necessitate maintaining an inventory of sizes and styles. Moreover, counters seldom truly conform for long to the last or foot shape, breaking down in service and perhaps consequently resulting in discomfort in wear and/or unsatisfactory appearance and shortened useful life. Toe portions of vamps have been stiffened, for example, by the use of thermoplastic applied as disclosed in U.S. Pat. Nos. 3,945,074 and 4,063,527 to mention only two of many.
In the prior art there have been attempts to inject stiffening adhesive between an extremity of a shoe upper and a liner or insert while placed over a last. In general such "one-shot" approaches have not been commercially acceptable largely for the reason that they lack the nice control required to produce the ultimate required shapes. The opposite sides of uppers alone may differ in thickness by as much as 0.040", and upper and lining combinations have thickness variation of up to about 0.060"; such non-uniformity raises very difficult if not impossible problems for a purely rigid mold shoe forming system. It will be appreciated, for instance, that in addition to catering for sizes, counter portions should be thicker in the back seam region and along the base region but then taper to a much reduced thickness along the top line of the upper and at the outer wing portions. The present invention accordingly recognizes the desirability of a two-stage solution, i.e. (1) introduction of thermoplastic resin to the preliminarily formed work with suitable distribution to be more completely effected by substantially universally applicable cooperative preforming and related implements, the main subject of the present invention, and (2) transition of the assembled upper, and preferably (though not necessarily) while the resin is still molten, for lasting in a suitable adjacent machine (for instance of the backpart molding type disclosed in U.S. Pat. No. 3,096,531) to impart final conforming shape to the stiffened upper placed on its last. Such two-stage making of shoes, as well as other products to be similarly stiffened and formed, is advantageous from a practical standpoint in that the first stage can be performed more quickly than the second and a cooling or dwell period is desirable in the latter to insure that deposited resin in not adversely redistributed. It is desirable that the upper "remember" its final conforming, but not its preforming in the initial stage.